The present invention relates to a recording/reproducing apparatus and a rotary head drum device, and particularly to a recording/reproducing apparatus and a rotary head drum device in which recording and/or reproducing is performed by winding a tape shaped recording medium around the periphery of a rotary drum and bringing a head fitted to the rotary drum into contact with the tape shaped recording medium.
Helical scan type recording/reproducing apparatuss are widely used as a VTR (Video Tape Recorder) or a data tape recorder. Such a recording/reproducing apparatus includes a rotary drum and a fixed drum, and a magnetic head is so fitted as to front on the outer peripheral surface of the rotary drum. A magnetic tape is helically wound around the outer peripheral surfaces of the rotary drum and the fixed drum, and the rotary drum is rotationally driven, whereby the magnetic head scans skewly on the magnetic tape. According to such a helical scan type recording/reproducing apparatus, mutually parallel tracks are sequentially formed on the magnetic tape in a direction inclined relative to the longitudinal direction of the magnetic tape, and recording and/or reproducing of signals is performed by such tracks.
FIG. 7 shows a major portion of such a helical scan type recording/reproducing apparatus, in which a pair of magnetic heads 2 are fitted to a rotary drum 1, for example, at positions spaced apart by 180 degrees in the circumferential direction. A roller guide 3 and an inclined guide 4 are disposed on the inlet side for introducing a magnetic tape 7, and a roller guide 5 and an inclined guide 6 are disposed on the outlet side of the magnetic tape 7.
In such an arrangement, the magnetic tape 7 is slowly fed in sliding contact on the outer periphery side of the rotary drum 1 while being guided by the roller guide 3 and the inclined guide 4, and is taken out of the rotary drum 1 by the inclined guide 6 and the roller guide 5. With the rotary drum 1 rotated, the magnetic head 2 is brought into sliding contact with the magnetic tape 7, and writing or reading of signals is performed by application of the principle of magnetic induction or the principle of electromagnetic induction.
In the helical scan type recording/reproducing apparatus using such a rotary drum 1, the rotary drum 1 is driven to rotate counterclockwise, namely, in the same direction as the feeding direction of the magnetic tape 7 as shown in FIG. 7. At this time, air is taken in as indicated by arrow 8 by the outer peripheral surface of the rotary drum 1, and the air penetrates into the space between the rotary drum 1 and the magnetic tape 7, forming an air film. Here, when the amount of the air is large, the magnetic tape 7 is swollen largely to the outer periphery side on the downstream side of the inclined guide 4 at the point where the magnetic tape 7 starts making contact with the magnetic head 2, as indicated by the two-dotted chain line in FIG. 7.
FIG. 8 shows the variation in the thickness of an air film formed between the outer peripheral surface of the rotary drum 1 and the magnetic tape 7 by the airflow indicated by arrow 8, from the inlet side to the outlet side of the magnetic tape 7. As is clear from the graph, the thickness of the air film is particularly large on the inlet side of the magnetic tape 7. Due to the large thickness value, the magnetic head 2 and the magnetic tape 7 are spaced apart largely from each other at the inlet side portion of the magnetic tape 7, so that the RF output waveform is lowered than a sufficient value at the starting side portion, as shown in FIG. 6.
In order to dissolve the lowering of the output due to taking-in of airflow 8 attendant on the rotation of the rotary drum 1, Japanese Patent Laid-open No. 2000-132890 discloses an apparatus in which an outer peripheral surface of the rotary drum 1 is provided with a plurality of grooves in the circumferential direction. Alternatively, Japanese Patent Laid-open No. 2000-251352 discloses an apparatus in which an air guide is skewly provided in the vicinity of the inclined guide 4 in proximity to the outer peripheral surface of the rotary drum 1.
The problem of floating of the magnetic tape 7 to the outer periphery side due to the airflow 8 mentioned above is rarely generated where the rotational speed of the rotary drum 1 is low. In addition, the floating to the outer periphery side can be prevented by giving a sufficient tension to the magnetic tape 7. In this case, therefore, it is needless to restrain the flowing-in of the airflow 8. When the rotational speed of the rotary drum 1 is raised in order to achieve a high transfer rate, however, the amount of floating of the magnetic tape on the inlet side increases, and this phenomenon cannot be dissolved by tape tension. This is because of the problem that the life of the magnetic tape is lowered when tape tension is raised under the condition where the rotational speed is high.
Therefore, it is necessary to lower the tape tension. Where the tape tension is low, the floating cannot be restrained by simply providing the outer peripheral surface of the rotary drum 1 with the grooves as disclosed in Japanese Patent Laid-open No. 2000-132890. An apparatus having a propeller type or an intermediate drum rotation type of drum construction in place of the combination of a rotary drum and a fixed drum is somewhat advantageous against the above-mentioned problems, but such an approach leads to a rise in cost on the construction basis or worsening of assemblability. Besides, such an approach is poor in reworkability, and is unsuitable for positive adoption.
An apparatus of providing a guide plate skewly at a position on the direct downstream side of an inlet-side inclined guide as disclosed in Japanese Patent Laid-open No. 2000-251352 suffers the problem that the air pressure at the portion on the upstream side of the guide plate is locally abnormally raised since the air taken in by the rotary drum is compressed by the guide plate. Besides, there is the problem that the air has a negative pressure at a position on the downstream side of the guide plate, so that it is impossible to stably control the air film.
The present invention has been made in view of the above-mentioned problems. Accordingly, it is an object of the present invention to provide a recording/reproducing apparatus and a rotary head drum device in which it is possible to reduce the thickness of the air film at the portion on the inlet side of a tape shaped recording medium and to control the thickness of the air film to be substantially uniform.
In accordance with one aspect of the present invention, there is provided a recording/reproducing apparatus, together with a rotary head drum device therefor, for performing recording and/or reproducing by winding a tape shaped recording medium around the periphery of a rotary drum and bringing one or more heads fitted to the rotary drum into contact with the tape shaped recording medium, wherein a guide plate is provided for restraining air flowing along the rotational direction of the rotary drum around the periphery of the rotary drum on the upstream side with respect to the rotational direction of the rotary drum in relation to the position where the head and the tape shaped recording medium start making contact with each other.
Here, an edge of the guide plate on the upstream side with respect to the rotational direction of the rotary drum may strip the airflow flowing in the rotational direction of the rotary drum and may release the stripped airflow to the side of the outer periphery. Of the guide plate, the edge on the upstream side with respect to the rotational direction of the rotary drum may be wedge-shaped, and the outer peripheral surface may be a guide surface for releasing the air. In addition, the guide plate may be provided with an extended portion for controlling the airflow flowing into the space between the outer peripheral surface of the rotary drum and the tape shaped recording medium via an end face of the rotary drum. Besides, the extended portion may be provided on an outside surface thereof with a rib for preventing vibration.
According to the recording/reproducing apparatus and the rotary head drum device, by restraining the airflow flowing into the space between the rotary drum and the tape shaped recording medium attendant on the rotation of the rotary drum, it is possible to largely reduce the thickness of the air film particularly at an inlet portion, and to make substantially uniform the thickness of the air film along the rotational direction of the rotary drum, whereby electromagnetic conversion efficiency particularly at the inlet portion can be prevented from being lowered.
In accordance with another aspect of the present invention, there is provided a recording/reproducing apparatus, together with a rotary head drum device therefor, including a rotary drum to which a head is fitted, and a fixed drum whose outer peripheral side is a guide surface for a tape shaped recording medium, the rotary drum and the fixed drum being combined so as to coaxially overlap with each other, and recording and/or reproducing being performed by helically winding the tape shaped recording medium around the outer peripheries of the rotary drum and the fixed drum and scanning the head fitted to the rotary drum on the tape shaped recording medium, wherein a guide plate is provided for restraining both an airflow caused to flow into the space between the rotary drum and the tape shaped recording medium by the rotation of the rotary drum and an airflow flowing into the space between the rotary drum and the tape shaped recording medium via an end face of the rotary drum and a side end of the tape shaped recording medium.
Here, the guide plate may be fixed on an outer peripheral portion of the rotary drum. The gap between the guide plate and the rotary drum is preferably in the range of 0.1 to 2 mm.
According to the recording/reproducing apparatus and the rotary head drum device, it is possible to restrain by the guide plate both the air introduced flowingly in the circumferential direction attendant on the rotation of the rotary drum and the air introduced into the space between the rotary drum and the tape shaped recording medium via an end face of the rotary drum, whereby evening of the air film along the rotational direction of the rotary drum is achieved.
The above arrangement contributes largely to stabilization of the air film, particularly in the case where the rotary drum is rotated at high speed, and it becomes unnecessary to increase needlessly the tape tension of the tape shaped recording medium, whereby elongation of the useful life of the tape shaped recording medium is contrived.
In a preferred mode of the present invention, a guide plate ranging from the surface of the rotary drum to an upper portion at a portion on the upper side of an upper-side edge of the tape shaped recording medium is provided at a surface portion of the rotary drum up to the vicinity of an inlet for the tape shaped recording medium where the head and the tape shaped recording medium start making contact with each other, in a portion on the rear side of the rotary drum disposed on the fixed drum where the rotary drum does not make contact with the tape shaped recording medium, and in the range from the inlet to about 60 degrees in the winding direction of the tape; by the guide plate, the airflow engulfed into the space between the rotary drum and the tape shaped recording medium by the rotation of the rotary drum is restrained
In a rotary drum having a large-diameter and high-speed rotation type rotary drum not lower than the VHS specification with a diameter of 62 mm. in the case where the rotational speed is not less than 5000 rpm, relative velocity to a magnetic tape is not less than 16 m/sec and the tension of the tape shaped recording medium is not more than 20 g, the air film at the tape inlet of the rotary drum becomes too thick in the radial direction of the rotary drum, so that it is difficult to restrain the air film by simply providing the outer peripheral surface of the rotary drum with more circumferential grooves or deepening the grooves.
However, with the guide plate according to the above mentioned embodiment, it is made possible to restrain at least the airflow penetrating to the lower side of the tape shaped recording medium wound around the rotary drum and the airflow engulfed to the surface of the rotary drum by a centrifugal force via an upper-side end face of the rotary drum, thereby largely contributing to restraining of the problem of the air film particularly at a high-speed rotation. In addition, the air film is made substantially uniform along the longitudinal direction of the tape shaped recording medium, and contact of the tape shaped recording medium particularly at the inlet-side portion is improved, so that it is possible to obtain an ideal RF waveform as shown in FIG. 5.